The present invention is directed to an improved anvil for a strapping machine. More particularly, the present invention is directed to a strapping machine anvil that has a vibrating member anvil with an offset eccentric link and captured bearings and a readily removable and maintainable vibrator pad support.
Strapping machines are in widespread use for securing straps around loads. One type of known strapper includes a strapping head and drive mechanism mounted within a frame. A chute is mounted to the frame, through which the strapping material is fed.
In a typical stationary strapper, the chute is mounted at about a work surface, and the strapping head is mounted to a horizontal or vertical portion (or perhaps an inclined portion) of the chute. The strapping or welding head provides a number of functions. First, the strapping head includes a gripper for gripping the strap during the course of a strapping operation. The strapping head also includes a cutter to cut the strap from a strap source or supply. Last, the strapping head includes a sealer to seal an overlying course of strapping material onto itself. This seal is commonly referred to as a weld and is effected by heating overlying courses of the strap by use of a vibrating element.
In one arrangement, to effect the seal or weld, an anvil is maintained rigidly against one of the courses of strap and a vibrating element located in the strapping head oscillates or vibrates against the other course of strap, thus creating friction and heat to effect the weld. The vibrating element is driven by a motor that is mounted to the body of the strapping head and is operably connected to the vibrating element. Such an arrangement is disclosed in Gerhart, U.S. Pat. No. 6,532,722, which patent is commonly owned with the present application and is incorporated herein by reference.
In known weld motor arrangements, the motor shaft has an eccentric fitting or bearing mounted thereto. The eccentric fitting is positioned in an elongated open slot in a connecting portion of the vibrating element. This arrangement permits a back-and-forth movement (or longitudinal movement) of the element to effect vibration. The vibrating element is permitted to move longitudinally, but is prevented from moving in a side-to-side (i.e., lateral) motion. However, in order to effect the longitudinal motion the elongated slot in which the eccentric fitting is positioned requires that the slot width (in the lateral direction) be equal to the two times the greatest dimension of the shaft center to the eccentric periphery. High friction areas thus result at the sides of the slot from use of such an eccentric drive. Although this arrangement does in fact function well, in order to assure proper operation of the eccentric, large amounts of lubricant are required.
The vibrating element resides in a slot in the anvil. Bearings are positioned between the element and the anvil walls to reduce friction due to movement of the element. The connection of the element to the eccentric is a linear connection. As such, in order to remove the vibrating element from the anvil, it is necessary to disassemble a significant potion of the head (removing the motor and/or anvil from the body) to perform maintenance or inspection of the vibrating element or vibrator pad.
Accordingly, there exists a need for a strapping machine strapping head that incorporates a reduced friction design for the weld motor to vibrating element connection. Desirably, such a connection is provided by an offset connecting link having integral, closed bearings and eliminates the need for open slotted regions to accommodate eccentric movement. More desirably, such a link is configured to permit readily removing the vibrating element from the anvil to inspect, maintain or replace the element or vibrator pad.